Hemodynamic determinants of the amplitude of the second heart sound.

Abstract

The relationship between the amplitude of the aortic component of the second heart sound and various hemodynamic parameters and their analog functions was systematically investigated in 26 dogs under morphine pentobarbital anesthesia. Simultaneous hemodynamic and phonocardiographic tracings were obtained using cardiac catheterization, high-speed recording, and analog computers. Changes in cardiodynamics were induced by: 1-epinephrine, levarterenol, isoproterenol, methoxamine, veratrine, Pitressin, atropine, histamine, serotonin, amyl nitrite, mechanical obstruction of the venae cavae, hemorrhage and establishing arterial venous shunts. The results showed that the amplitude of the aortic second heart sound is not directly related to aortic pressures, aortic-to-left ventricular differential pressures, or to the derivatives of these pressures at the time of the dicrotic notch. Only the peak rate of development of the aortic-to-left ventricular differential pressure gradient (first derivative maximum) had a consistent relationship to aortic second-sound amplitude. The correlation coefficient of 0.978 suggests a direct physical relationship which is related to mass acceleration functions in the aorta.